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View Full Version : full SD backup - why so slow?


Dan Lester
02-23-2014, 01:08 PM
I've used SD for many years. Fabulous. I do smart backups every night while I sleep, and ... it just works.

But today I wanted to back up to an entirely separate drive -- a full backup from an iMac 10.6.8 to a (freshly erased, and Mac OS Extended (Journaled) formatted) Maxtor 4 5400rpm IDE disk in a Sabrent enclosure over USB2. I'm watching the SD backup slog along at 1Mb/s! That can't be right, can it? Of course, it's a slow disk, and a slow bandwidth, but not THAT slow.

So my question is, if that isn't right, what diagnostics can I do to understand why it's so slow? Is there a SD "speed FAQ" somewhere that looks at how system trades affect backup speed?

dnanian
02-23-2014, 01:17 PM
Seems likely that your USB2 drive is running at USB1 speeds...

Dan Lester
02-24-2014, 12:35 PM
Somewhat frustratingly, this looks to be the case. Just manually moving a file to this unit runs at ~1MB/s. That's USB1 speed.

This probably isn't the right forum to ask this, but this enclosure is rated as USB2 (and the computer driving it is certainly USB2). Is fallback from USB2 to USB1 a recognized failure mode for disk enclosure electronics?

dnanian
02-24-2014, 01:13 PM
It usually means something that's connected along with it is forcing it down to USB 1 speeds. Is this connected directly to the Mac? Perhaps try using a different cable?

Dan Lester
02-24-2014, 02:32 PM
Dave, you are precisely right, and I am SO embarrassed. I now realize that the enclosure was connected to my Mac through a USB1 rated dongle. Now that I plug it in directly, everything is FAST. I guess a lesson here, which I had never fully appreciated, is the enormity of the difference between USB1.1 and USB2.

I don't mind USB1.1 for many things, but moving GB of data (as in, backups) is NOT one of those things.

dnanian
02-24-2014, 02:38 PM
Glad you're all set now, Dan (and sorry for the typo in the original response...)

Anne R
10-26-2014, 04:45 PM
I just experienced the same problem, seemingly not due to the cable connection which is Firewire.
Backup running 2 hours & getting nowhere!
Running SuperDuper Version 93
MacBook Pro Software Mac OS X Lion 10.7.5 (11G63), 4GB
Any ideas / solutions?

dnanian
10-26-2014, 05:13 PM
I've replied to your email, Anne, so let's continue there.